The parting line must occur along the line round the position of maximum dimension when viewed in the draw direction.[pye] Many applications (seals, tight running molded parts) that require precision for shape control, call for removal of flashes. Secondary operations are thus employed, in addition to high precision molding dies to remove these flashes. Many molders will repair or even replace the mold tooling so that the flash is reduced to an acceptable tolerance or eliminated altogether. Secondary operations to remove parting line flash include hand trimming, vibratory tumbling, media blasting and cryogenic deflashing.
Flashes are known to improve sealing between mating faces in some instances (Fuel tank seals, hydraulic power steering gear, etc.), and thus flashes are permitted to some extent in special cases.